video: This video shows ape eye movements when watching a video showing an aggressive person in an ape suit coming out from one of two identical doors. The eye movements are again tracked 24 hours later. view more
Credit: Fumihiro Kano, and Kumamoto Sanctuary, Wildlife Research Center, Kyoto University
Remember the scene in the classic movie Alien, when that creepiest of creatures bursts out of John Hurt's belly as he writhes in pain? Well, according to a study reported in the Cell Press journal Current Biology on September 17, great apes are pretty good at remembering and anticipating memorable events they've seen on-screen too--even when they've seen the event only once.
"When you watch a shocking, emotional event in a movie, you remember the event well, and later on, when you watch the same movie, you anticipate the event," says Fumihiro Kano of Kyoto University in Japan. "Thanks to a recent advance of state-of-the-art eye-tracking technologies, we could examine event anticipation by great apes while watching a movie by means of 'anticipatory looks' to the impending events."
Great apes are already known to have excellent long-term memory skills. However, most studies have examined those skills in the context of food-hiding tests, in which apes see food being hidden and then later retrieve the foods. No one had tested to see whether they could also remember events just by watching them in other contexts.
To find out, the researchers made two short films starring themselves and then showed them to six chimpanzees and six bonobos while tracking their eye movements. In one movie, an aggressive person in an ape suit came out from one of two identical doors. In the other film, a human actor grabbed one of two objects and attacked the ape-like character with it.
The eye-tracking data showed that animals anticipated what they were about to see after a single viewing of the movie. On a second viewing of the first movie, the apes directed their attention to the door where they knew the person dressed as an ape would appear. While watching the second film again, the animals looked in anticipation at the object they knew would soon be used as a kind of weapon, even when that object was placed in a different location than they'd seen earlier.
The findings show that great apes encoded information from the film into their long-term memories and later used that information to anticipate events that were about to happen. And all of that memory is reflected right there in the apes' eyes.
Something else surprised and interested the researchers: the apes really seemed to enjoy the movies. "We were giving juice while showing the videos to them," Kano says, "but some of them even forgot to drink [the] juice and stared at the movies!"
The researchers say they now plan to use anticipatory looks to examine other high-level cognitive functions in the apes, such as the ability to understand that others have beliefs, desires, intentions, and perspectives that differ from their own.
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This study was in part funded by JSPS KAKENHI, MEXT KAKENHI, JSPSLGP-U04, JSPS core-to-core type A CCSN, and MEXT-PRI-Human Evolution.
Current Biology, Kano and Hirata: "Great Apes Make Anticipatory Looks Based on Long-Term Memory of Single Events" http://dx.doi.org/10.1016/j.cub.2015.08.004
Current Biology, published by Cell Press, is a bimonthly journal that features papers across all areas of biology. Current Biology strives to foster communication across fields of biology, both by publishing important findings of general interest and through highly accessible front matter for non-specialists. For more information please visit http://www.cell.com/current-biology. To receive media alerts for Current Biology or other Cell Press journals, contact press@cell.com.
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Current Biology